Due to growing environmental concerns and economic and political requirements, the integration of renewable energy into the power grid has become a growing trend. Renewable energy sources have the potential to lead to a significant reduction in fossil fuel consumption and carbon dioxide emissions. Renewable energy generation, however, is typically non-dispatchable because it is often operated at the maximum output due to the low marginal cost of renewable energy. In addition, the available output of renewable generation is very variable and uncertain due to the intermittency of renewable energy.
Large-scale integration of renewable energy into the power grid substantially increases the need for operational reserves. At the same time, the total system inertia, as well as contingency reserve, is decreasing as conventional generation is gradually displaced by non-dispatchable renewable generation. Therefore, it becomes extremely difficult for a system operator to maintain the stability and reliability of the power grid. If operational reserves are required to be provided by conventional generation for stability reasons, it diminishes the net carbon benefit from renewables, reduces generation efficiency, and becomes economically untenable. Hence, renewable penetration is still limited due to the lack of appropriate technologies that are able to reliably and affordably manage the dynamic variability introduced by renewable generation.
Demand-side approaches can help alleviate some of the instability resulting from renewable generation sources. Conventionally, demand-side loads are treated as passive and non-dispatchable, but demand-side approaches such as management of flexible loads have begun to be introduced. Such approaches, however, typically do not produce a frequency response curve that closely matches the desired curve, which can cause additional instability. Further, conventional demand-side approaches can over- or undercompensate by managing too many or too few loads.